I say some.
I do workout during the holidays, but they are shorter and I workout with the workout DVD's (because I hate jogging and taking long walk in the cold weather...BRRR!).
So my workouts are a little bit "lazier" during this time, until late February, then I'll go back to my regular jogging and long walk outdoors.
Yeah, it's not really the parties that impact my workouts, it tends to be more just I don't take time away from family on the actual holidays--right around christmas eve, day, and New Year's. Elsewise, I'm usually on track!
I say a little. I use the gym at my university and the whole campus will be closed for a week or two. I'll have to see if I can get a couple of free 7-day trials at other gyms for that time.
How much do the holidays REALLY affect your fitness schedule?
10 Pounds DOWN!